U.S. patent number 11,180,843 [Application Number 16/816,181] was granted by the patent office on 2021-11-23 for method for manufacturing deposition mask, method for manufacturing display device and deposition mask.
This patent grant is currently assigned to TOPPAN PRINTING CO., LTD.. The grantee listed for this patent is TOPPAN PRINTING CO., LTD.. Invention is credited to Naoko Mikami, Shunsuke Sato, Reiji Terada.
United States Patent |
11,180,843 |
Sato , et al. |
November 23, 2021 |
Method for manufacturing deposition mask, method for manufacturing
display device and deposition mask
Abstract
A method includes: sandwiching a plastic layer between a glass
substrate and a metal plate made of an iron-nickel alloy and
joining the metal plate to the glass substrate with the plastic
layer in between; forming a mask portion including a plurality of
mask holes from the metal plate; joining a surface of the mask
portion that is opposite to a surface of the mask portion that is
in contact with the plastic layer to a mask frame, which has a
higher rigidity than the mask portion and is in a shape of a frame
surrounding the mask holes of the mask portion; and peeling off the
plastic layer and the glass substrate from the mask portion.
Inventors: |
Sato; Shunsuke (Tokyo,
JP), Terada; Reiji (Tokyo, JP), Mikami;
Naoko (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOPPAN PRINTING CO., LTD. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
TOPPAN PRINTING CO., LTD.
(Tokyo, JP)
|
Family
ID: |
1000005948386 |
Appl.
No.: |
16/816,181 |
Filed: |
March 11, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200208251 A1 |
Jul 2, 2020 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
PCT/JP2018/034083 |
Sep 13, 2018 |
|
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Sep 15, 2017 [JP] |
|
|
JP2017-178223 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C
14/588 (20130101); C23C 14/5813 (20130101); H01L
51/0011 (20130101); C23C 14/042 (20130101) |
Current International
Class: |
H01L
51/00 (20060101); C23C 14/58 (20060101); C23C
14/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
106350768 |
|
Jan 2017 |
|
CN |
|
2017-145491 |
|
Aug 2017 |
|
JP |
|
WO 2017/057621 |
|
Apr 2017 |
|
WO |
|
Other References
International Search Report and Written Opinion with translation of
international Search Report for PCT Application PCT/JP2018/034083
dated Nov. 6, 2018, 9 pages. cited by applicant.
|
Primary Examiner: Oh; Jaehwan
Attorney, Agent or Firm: Squire Patton Boggs (US) LLP
Claims
The invention claimed is:
1. A method for manufacturing a vapor deposition mask including a
mask portion that is formed from a metal plate made of an
iron-nickel alloy and has a plurality of mask holes, the method
comprising: sandwiching a plastic layer between a glass substrate
and a metal plate made of an iron-nickel alloy and joining the
metal plate to the glass substrate with the plastic layer in
between; forming a mask portion including a plurality of mask holes
from the metal plate; joining a surface of the mask portion that is
opposite to a surface of the mask portion that is in contact with
the plastic layer to a mask frame, which has a higher rigidity than
the mask portion and is in a shape of a frame surrounding the mask
holes of the mask portion; and peeling off the plastic layer and
the glass substrate from the mask portion.
2. The method for manufacturing a vapor deposition mask according
to claim 1, wherein peeling off the plastic layer and the glass
substrate includes peeling off the glass substrate from the plastic
layer by irradiating an interface between the plastic layer and the
glass substrate with a laser beam having a wavelength that passes
through the glass substrate and is absorbed by the plastic layer,
and peeling off the plastic layer from the mask portion by
dissolving the plastic layer using a chemical solution after
peeling off the glass substrate from the plastic layer.
3. The method for manufacturing a vapor deposition mask according
to claim 2, wherein at the wavelength of the laser beam, the glass
substrate has a higher transmittance than the plastic layer.
4. The method for manufacturing a vapor deposition mask according
to claim 3, wherein the wavelength of the laser beam is between 308
nm and 355 nm inclusive, the transmittance of the glass substrate
at the wavelength is greater than or equal to 54%, and the
transmittance of the plastic layer at the wavelength is less than
or equal to 1%.
5. The method for manufacturing a vapor deposition mask according
to claim 1, wherein the mask frame is made of an iron-nickel alloy,
and a ratio of a thickness of the mask frame to a thickness of the
mask portion is greater than or equal to 2.
6. The method for manufacturing a vapor deposition mask according
to claim 5, wherein the thickness of the mask frame is between 50
.mu.m and 200 .mu.m inclusive, the thickness of the mask portion is
between 3 .mu.m and 5 .mu.m inclusive, and forming the mask portion
includes forming the mask holes such that 700 or more and 1,000 or
less mask holes are arranged per inch in a direction along a
surface of the mask portion.
7. The method for manufacturing a vapor deposition mask according
to claim 1, wherein joining the metal plate to the glass substrate
with the plastic layer in between includes joining the metal plate
having a thickness of greater than or equal to 10 .mu.m to the
glass substrate with the plastic layer in between, and the method
further comprises etching the metal plate before the mask portion
is formed from the metal plate to reduce a thickness of the metal
plate to half or less of a thickness of the metal plate before
etching.
8. The method for manufacturing a vapor deposition mask according
to claim 1, wherein the plastic layer is made of polyimide.
9. The method for manufacturing a vapor deposition mask according
to claim 1, wherein the metal plate includes a first surface and a
second surface, the method further comprises etching the metal
plate from the first surface before joining the metal plate to the
glass substrate, joining the metal plate to the glass substrate
includes joining a surface obtained after the first surface is
etched to the glass substrate with the plastic layer in between,
and the method further comprises etching the metal plate from the
second surface after the metal plate is joined to the glass
substrate.
Description
BACKGROUND
The present disclosure relates to a method for manufacturing a
vapor deposition mask, a method for manufacturing a display device,
and a vapor deposition mask.
A vapor deposition mask has a contact surface and a non-contact
surface. The contact surface is brought into contact with the vapor
deposition target, such as a substrate, and the non-contact surface
is opposite to the contact surface. The vapor deposition mask has a
plurality of mask holes. Each mask hole extends through the vapor
deposition mask from the non-contact surface to the contact surface
and includes a non-contact opening, which is in the non-contact
surface and through which the vapor deposition material enters, and
a contact opening, which is in the contact surface and faces the
vapor deposition target. The vapor deposition material enters
through the non-contact opening and proceeds through the contact
opening so as to be deposited on the vapor deposition target. This
forms a pattern corresponding to the position and shape of the
contact opening on the vapor deposition target (see Japanese
Laid-Open Patent Publication No. 2017-145491, for example).
To improve the accuracy of the position and other features of
patterns, techniques have been used to manufacture vapor deposition
masks in which each mask hole has a passage area that decreases
monotonically from the non-contact opening to the contact opening.
Further, in recent years, there has been a need for a shorter
distance between the non-contact opening and the contact opening,
that is, a thinner vapor deposition mask, to improve the uniformity
of the film thickness of the pattern.
However, a thinner vapor deposition mask typically fails to have
sufficient mechanical durability, considerably increasing the
difficulty of handling the vapor deposition mask. Accordingly,
there is a strong need for a technique that achieves both the
improvement in the accuracy of features of patterns and the
improvement in the handleability of vapor deposition masks.
SUMMARY
It is an objective of the present disclosure to provide a method
for manufacturing a vapor deposition mask, a method for
manufacturing a display device, and a vapor deposition mask that
achieve both the improvement in the accuracy of the structure of
patterns formed by vapor deposition and the improvement in the
handleability of the vapor deposition mask.
To achieve the foregoing objective, a method for manufacturing a
vapor deposition mask including a mask portion that is formed from
a metal plate made of an iron-nickel alloy and has a plurality of
mask holes is provided. The method includes: sandwiching a plastic
layer between a glass substrate and a metal plate made of an
iron-nickel alloy and joining the metal plate to the glass
substrate with the plastic layer in between; forming a mask portion
including a plurality of mask holes from the metal plate; joining a
surface of the mask portion that is opposite to a surface of the
mask portion that is in contact with the plastic layer to a mask
frame, which has a higher rigidity than the mask portion and is in
a shape of a frame surrounding the mask holes of the mask portion;
and peeling off the plastic layer and the glass substrate from the
mask portion.
With this configuration, the plastic layer and the glass substrate
support the mask portion having a plurality of through-holes in the
process of manufacturing the vapor deposition mask. In addition,
the mask frame supports the mask portion in the vapor deposition
mask. This allows the mask portion to be thinner than that in a
configuration in which the vapor deposition mask consists only of
the mask portion. Consequently, the shortened distance from one
opening to the other of each through-hole improves the accuracy of
the structure of the pattern, while the rigidity of the mask frame
improves the handleability of the vapor deposition mask.
In the above-described method for manufacturing a vapor deposition
mask, peeling off the plastic layer and the glass substrate may
include: peeling off the glass substrate from the plastic layer by
irradiating an interface between the plastic layer and the glass
substrate with a laser beam having a wavelength that passes through
the glass substrate and is absorbed by the plastic layer; and
peeling off the plastic layer from the mask portion by dissolving
the plastic layer using a chemical solution after peeling off the
glass substrate from the plastic layer.
This configuration peels off the glass substrate from the plastic
layer by irradiation with the laser beam and also peels off the
plastic layer from the mask portion by dissolving the plastic layer
using a chemical solution. This reduces the external force acting
on the mask portion, as compared to a configuration that applies an
external force to the laminate of the glass substrate, the plastic
layer, and the mask portion to cause interface failure to peel off
the glass substrate and the plastic layer from the mask portion. As
a result, the peeling of the plastic layer and the glass substrate
is less likely to deform the mask portion, and ultimately less
likely to deform the through-holes in the mask portion.
In the above-described method for manufacturing a vapor deposition
mask, at the wavelength of the laser beam, the glass substrate may
have a higher transmittance than the plastic layer.
This configuration increases the efficiency in heating the section
of the plastic layer that forms the interface between the glass
substrate and the plastic layer, as compared to a configuration in
which the plastic layer has a higher transmittance than the glass
substrate.
In the above-described method for manufacturing a vapor deposition
mask, the wavelength of the laser beam may be between 308 nm and
355 nm inclusive. Also, the transmittance of the glass substrate at
the wavelength may be greater than or equal to 54%, and the
transmittance of the plastic layer at the wavelength may be less
than or equal to 1%.
In this configuration, the glass substrate allows more than half
the light quantity of laser beam applied to the glass substrate to
pass through, and the plastic layer absorbs most of the laser beam
that has passed through the glass substrate. This further increases
the efficiency in heating the section of the plastic layer forming
the interface between the glass substrate and the plastic
layer.
In the above-described method for manufacturing a vapor deposition
mask, the mask frame may be made of an iron-nickel alloy, and a
ratio of a thickness of the mask frame to a thickness of the mask
portion may be greater than or equal to 2.
In this configuration, both of the mask portion and the mask frame
are made of an iron-nickel alloy, and the mask frame is at least
twice as thick as the mask portion. This enhances the mechanical
strength of the vapor deposition mask. Further, when vapor
deposition is performed using the vapor deposition mask, the mask
portion is unlikely to warp, which would be otherwise caused by a
difference in thermal expansion coefficient between the mask frame
and the mask portion. This avoids reduction in the accuracy of the
shape of pattern formed using the vapor deposition mask.
In the above-described method for manufacturing a vapor deposition
mask, the thickness of the mask frame may be between 50 .mu.m and
200 .mu.m inclusive, and the thickness of the mask portion may be
between 3 .mu.m and 5 .mu.m inclusive. Also, forming the mask
portion may include forming the mask holes such that 700 or more
and 1,000 or less mask holes are arranged per inch in a direction
along a surface of the mask portion.
In this configuration, even when the thickness of the mask portion
is extremely thin, the mask frame that is at least ten times
thicker than the mask portion avoids reduction in the overall
mechanical strength of the vapor deposition mask.
In the above-described method for manufacturing a vapor deposition
mask, joining the metal plate to the glass substrate with the
plastic layer in between may include joining the metal plate having
a thickness of greater than or equal to 10 .mu.m to the glass
substrate with the plastic layer in between. The method may further
include etching the metal plate before the mask portion is formed
from the metal plate to reduce a thickness of the metal plate to
half or less of a thickness of the metal plate before etching.
In this configuration, the metal plate has a higher rigidity than
the mask portion of the vapor deposition mask. This facilitates the
joining of the metal plate to the glass substrate as compared to a
configuration in which the metal plate that is joined to the glass
substrate has the same thickness as the mask portion.
In the above-described method for manufacturing a vapor deposition
mask, the plastic layer may be made of polyimide.
In this configuration, the metal plate, the plastic layer, and the
glass substrate have similar thermal expansion coefficients.
Consequently, in the process of manufacturing the vapor deposition
mask, heating the laminate of the metal plate, the plastic layer,
and the glass substrate is unlikely to warp the laminate, which
would be otherwise caused by a difference in thermal expansion
coefficient between the layers of the laminate.
In the above-described method for manufacturing a vapor deposition
mask, the metal plate may include a first surface and a second
surface. The method may further include etching the metal plate
from the first surface before joining the metal plate to the glass
substrate. Also, joining the metal plate to the glass substrate may
include joining a surface obtained after the first surface is
etched to the glass substrate with the plastic layer in between.
The method may further include etching the metal plate from the
second surface after the metal plate is joined to the glass
substrate.
In this configuration, etching both the first and second surfaces
of the metal plate reduces the thickness of the metal plate and
also reduces the residual stress of the metal plate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing the structure of a mask device
according to one embodiment.
FIG. 2 is a cross-sectional view partially showing the structure of
a mask portion.
FIG. 3 is a cross-sectional view partially showing the joining
structure between an edge of a mask portion and a mask frame.
FIGS. 4A and 4B are a plan view and a cross-sectional view of the
structure of a vapor deposition mask, showing the relationship
between the number of mask holes in the vapor deposition mask and
the number of mask holes in each mask portion.
FIGS. 5A to 5F are process diagrams for illustrating a method for
manufacturing a vapor deposition mask according to one embodiment,
each showing one step in the process.
FIGS. 6A to 6C are process diagrams for illustrating a method for
manufacturing a vapor deposition mask according to one embodiment,
each showing one step in the process.
FIG. 7 is a graph showing the relationship between the wavelength
of a laser beam and the amount of displacement in test
examples.
FIG. 8 is a graph showing the relationship between the wavelength
of light and the transmittance of each glass substrate in test
examples.
FIG. 9 is a graph showing the relationship between the wavelength
of light and the transmittance of each plastic layer in test
examples.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Referring to FIGS. 1 to 9, embodiments of a method for
manufacturing a vapor deposition mask, a method for manufacturing a
display device, and a vapor deposition mask are now described. In
the following descriptions, the structure of a mask device, the
joining structure of the mask portions of the mask device, the
number of the mask portions, a method for manufacturing a vapor
deposition mask, and test examples are explained in this order.
[Structure of Mask Device]
Referring to FIGS. 1 and 2, the structure of a mask device is now
described.
As shown in FIG. 1, a mask device 10 includes a main frame 20 and a
plurality of vapor deposition masks 30. The main frame 20 has a
rectangular frame shape for supporting the vapor deposition masks
30. The main frame 20 is attached to a vapor deposition apparatus
for performing vapor deposition. The main frame 20 has main frame
holes 21, which are equal in number to the vapor deposition masks
30. Each main frame hole 21 extends through the main frame 20 in
substantially the entire area where a vapor deposition mask 30 is
placed.
Each vapor deposition mask 30 includes a mask frame 31 and mask
portions 32. Each mask frame 31 has the shape of a planar strip and
supports the mask portions 32. The mask frame 31 is attached to the
main frame 20. The mask frame 31 has mask frame holes 33, which are
equal in number to the mask portions 32. Each mask frame hole 33
extends through the mask frame 31 in substantially the entire area
where a mask portion 32 is placed. The mask frame 31 has a higher
rigidity than the mask portions 32 and has a frame shape
surrounding the mask frame holes 33. The mask frame 31 has inner
edge sections defining the mask frame holes 33. The mask portions
32 are fixed to the inner edge sections by welding or adhesion.
As shown in FIG. 2, each mask portion 32 consists of a mask sheet
32S. The mask sheet 32S may be a single metal sheet or a multilayer
metal sheet.
The metal sheet forming the mask sheet 32S is made of an
iron-nickel alloy. The material of the metal sheet may be an
iron-nickel alloy containing at least 30 mass % of nickel. Among
iron-nickel alloys, Invar, which is an alloy mainly composed of an
alloy containing 36 mass % of nickel and 64 mass % of iron, is
preferably used for the metal sheet. When the principal component
of the metal sheet is the alloy of 36 mass % of nickel and 64 mass
% of iron, the remainder of the metal sheet may contain additives
such as chromium, manganese, carbon, and cobalt.
When the mask sheet 32S is an Invar sheet, the mask sheet 32S has a
thermal expansion coefficient of about 1.2.times.10.sup.-6/.degree.
C., for example. The mask sheet 32S having such a thermal expansion
coefficient allows the degree of thermal expansion of the mask
portion 32 to match that of the glass substrate. Thus, a glass
substrate may be suitably used as the target of vapor deposition
performed using the mask device 10.
The mask sheet 32S includes a mask front surface 32F and a mask
back surface 32R, which is opposite to the mask front surface 32F.
The mask front surface 32F faces the vapor deposition source in a
vapor deposition apparatus. The mask back surface 32R is in contact
with the vapor deposition target, such as a glass substrate, in the
vapor deposition apparatus. The mask back surface 32R is an example
of a contact surface, and the mask front surface 32F is an example
of a non-contact surface.
The mask sheet 32S may have a thickness of between 1 .mu.m and 15
.mu.m inclusive. In particular, when the thickness of the mask
sheet 32S is less than or equal to 5 .mu.m, mask holes 32H, which
are an example of through-holes formed in the mask sheet 32S, can
have a depth of less than or equal to 5 .mu.m. Such a thin mask
sheet 32S reduces the area in the vapor deposition target that is
hidden by the vapor deposition mask 30 as viewed from the vapor
deposition particles traveling toward the mask sheet 32S, in other
words, reduces the shadow effect.
The mask sheet 32S having a thickness of between 3 .mu.m and 5
.mu.m inclusive can have mask holes 32H that are spaced apart from
one another in a plan view of the mask front surface 32F and usable
to manufacture a high-resolution display device having a resolution
of between 700 ppi and 1,000 ppi inclusive. The mask sheet 32S
having a thickness of between 10 .mu.m and 15 .mu.m inclusive can
have mask holes 32H that are spaced apart from one another in a
plan view of the mask front surface 32F and usable to manufacture a
low-resolution display device having a resolution of between 300
ppi and 400 ppi inclusive.
Each mask portion 32 has a plurality of mask holes 32H extending
through the mask sheet 32S. The hole side surface defining each
mask hole 32H is semicircular and curved outward of the mask hole
32H as viewed in a cross-section along the thickness direction of
the mask sheet 32S.
The mask front surface 32F includes front surface openings H1,
which are openings of the mask holes 32H. The mask back surface 32R
includes back surface openings H2, which are openings of the mask
holes 32H. Each front surface opening H1 is an example of a first
opening, and each back surface opening H2 is an example of a second
opening. In a plan view of the mask front surface 32F, the front
surface opening H1 is larger in size than the back surface opening
H2. Each mask hole 32H is a passage for the vapor deposition
particles sublimated from the vapor deposition source. The vapor
deposition particles sublimated from the vapor deposition source
travel in the mask hole 32H from the front surface opening H1
toward the back surface opening H2. The mask hole 32H having the
front surface opening H1 that is larger than the back surface
opening H2 reduces the shadow effect for the vapor deposition
particles entering through the front surface opening H1.
In the mask front surface 32F, each front surface opening H1 is
spaced apart from the other front surface openings H1. In other
words, in the mask front surface 32F, each front surface opening H1
is not connected to the other front surface openings H1. Thus, in a
plan view of the mask front surface 32F, the sections of the mask
portion 32 located between the front surface openings H1 are
unlikely to be thinner than the section of the mask portion 32 that
is free of mask holes 32H. This avoids reduction in mechanical
strength of the mask portion 32. If one front surface opening H1 is
connected to another front surface opening H1 in the mask front
surface 32F, the section where the two front surface openings H1
overlap would be thinner than the section of the mask portion 32
that is free of mask holes 32H. This reduces the mechanical
strength of the mask portion 32 as compared to the configuration in
which each front surface opening H1 is spaced apart from the other
front surface openings H1.
When the mask portion 32 has a thickness of between 3 .mu.m and 5
.mu.m inclusive, mask holes 32H that are usable to manufacture a
high-resolution display device as described above can be formed
simply by wet-etching the mask sheet 32S from the mask front
surface 32F. Further, when the mask portion 32 has a thickness of
between 10 .mu.m and 15 .mu.m inclusive, mask holes 32H that are
usable to manufacture a low-resolution display device as described
above can be formed simply by wet-etching the mask sheet 32S from
the mask front surface 32F. That is, in either case, it is not
necessary to wet-etch the mask sheet 32S from the mask back surface
32R.
In contrast, if a thicker mask sheet 32S is used to form a vapor
deposition mask 30 for the manufacturing of a display device having
a certain resolution, this mask sheet 32S needs to be wet-etched
from both the mask front surface 32F and the mask back surface 32R.
When the mask sheet 32S is wet-etched from both the mask front
surface 32F and the mask back surface 32R, each mask hole 32H has a
shape in which a front surface recess, which includes a front
surface opening H1, and a back surface recess, which includes the
back surface opening H2, are connected to each other at the center
of the mask portion 32 in the thickness direction. In each mask
hole 32H, a section where the front surface recess is connected to
the back surface recess is referred to as a connection section. The
area of the mask hole 32H along the direction parallel to the mask
front surface 32F is smallest in the connection section. The
distance between the connection section and the back surface
opening H2 in the mask hole 32H is referred to as a step height. A
greater step height increases the shadow effect described above. In
contrast, the mask portion 32 described above has zero step height.
As such, the mask portion 32 advantageously limits the shadow
effect.
[Mask Portion Joining Structure]
Referring to FIG. 3, the cross-sectional structure of the joining
between a mask portion 32 and a mask frame 31 is now described.
As shown in FIG. 3, each mask sheet 32S has an outer edge section
32E, which includes the edge of the mask sheet 32S. The outer edge
section 32E of the mask sheet 32S includes a region that is free of
mask holes 32H and extends continuously along the edge of the mask
sheet 32S. The mask front surface 32F of the outer edge section 32E
is joined to the mask frame 31.
The mask frame 31 includes inner edge sections 31E, which define
mask frame holes 33, a frame back surface 31R, which faces the mask
sheet 32S, and a frame front surface 31F, which is opposite to the
frame back surface 31R. Each inner edge section 31E includes a part
of the frame back surface 31R and a part of the frame front surface
31F. The thickness T31 of the mask frame 31, that is, the distance
between the frame back surface 31R and the frame front surface 31F,
is greater than the thickness T32 of the mask sheet 32S. This
allows the mask frame 31 to have a higher rigidity than the mask
sheet 32S. In particular, the mask frame 31 has a high rigidity
that limits sagging of the inner edge section 31E by its own weight
and displacement of the inner edge section 31E toward the mask
portion 32.
The mask frame 31 is preferably made of an iron-nickel alloy, more
preferably an iron-nickel alloy that is used as the principal
component of the mask sheet 32S. That is, the mask frame 31 is
preferably made of Invar. The mask frame 31 is preferably at least
twice as thick as the mask portion 32.
The frame back surface 31R of each inner edge section 31E has a
joining section 30BN where the mask front surface 32F is joined to
the mask frame 31. The joining section 30BN extends continuously or
intermittently along substantially the entire circumference of the
inner edge section 31E. The joining section 30BN may be a welding
mark formed by welding the frame back surface 31R to the mask front
surface 32F. Alternatively, the joining section 30BN may be a
joining layer that is formed separately from the mask frame 31 and
the mask portion 32 to join the frame back surface 31R to the mask
front surface 32F.
When each mask frame 31 is joined to the main frame 20, the main
frame 20 applies stress to the mask frame 31 that pulls the mask
frame 31 outward. In this step, the mask frame 31 may be joined to
the main frame 20 such that the ends of the mask frame 31 in the
extending direction extend outward beyond the main frame 20.
The frame back surface 31R is a plane including the joining section
30BN and extends outward of the mask sheet 32S from the mask front
surface 32F of the outer edge section 32E. In other words, the
inner edge section 31E has a planar structure that virtually
extends the mask front surface 32F outward, so that the inner edge
section 31E extends from the mask front surface 32F of the outer
edge section 32E toward the outside of the mask sheet 32S.
Accordingly, in the area in which the frame back surface 31R
extends outward beyond the mask sheet 32S, a space V, which
corresponds to the thickness of the mask sheet 32S, is likely to be
created around the mask sheet 32S. This limits physical
interference between the vapor deposition target S and the mask
frame 31 around the mask sheet 32S.
[Number of Mask Portions]
With reference to FIG. 4, the relationship between the number of
mask holes 32H in a vapor deposition mask 30 and the number of mask
holes 32H in a mask portion 32 is now described.
As shown in FIG. 4A, each mask frame 31 may include three mask
frame holes 33, which are an example of a plurality of mask frame
holes 33. As shown in FIG. 4B, each vapor deposition mask 30
includes one mask portion 32 for each mask frame hole 33.
Specifically, the inner edge section 31E defining a first mask
frame hole 33A is joined to a first mask portion 32A. The inner
edge section 31E defining a second mask frame hole 33B is joined to
a second mask portion 32B. The inner edge section 31E defining a
third mask frame hole 33C is joined to a third mask portion
32C.
The vapor deposition mask 30 is used repeatedly for a plurality of
vapor deposition targets. Thus, the position and structure of the
mask holes 32H in the vapor deposition mask 30 need to be highly
accurate. When the number of mask holes 32H required in one mask
frame 31 is divided into three mask portions 32 as described above,
the following advantages are achieved. That is, in case one of the
mask portions 32 is partially deformed, the size of a new mask
portion 32 for replacing the deformed mask portion 32 may be
reduced, as compared to a structure in which all the mask holes 32H
are formed in one mask portion 32. In addition, the consumption of
various materials associated with the manufacturing and repair of
the vapor deposition mask 30 may be lowered.
The structure of the mask holes 32H is inspected preferably while
the mask portions 32 are joined to the mask frame 31. For this
reason, the joining section 30BN preferably has a configuration
that allows for replacement of a deformed mask portion 32 with a
new mask portion 32. Thus, one mask frame 31 can be used for a
plurality of mask portions 32, and different mask portions 32 can
be inspected using one mask frame 31. In addition, a thinner mask
sheet 32S of the mask portion 32 and smaller mask holes 32H tend to
reduce the yield of the mask portion 32. Thus, the structure in
which each of the mask frame holes 33 has one mask portion 32 is
particularly suitable for a vapor deposition mask 30 that requires
a high definition.
In the mask frame 31, the mask frame holes 33 form a mask hole row.
The mask frame 31 is not limited to the configuration with one mask
hole row and may include a plurality of mask hole rows. That is,
the vapor deposition mask 30 may include a plurality of rows of
mask portions 32.
[Method for Manufacturing Vapor Deposition Mask]
Referring to FIGS. 5 and 6, a method for manufacturing the vapor
deposition mask 30 is now described. FIG. 5 shows the step of
preparing a substrate for producing mask portions 32 to the step of
producing the mask portions 32. FIG. 6 shows the step of joining
the mask portions 32 to the mask frame 31 to the step of removing
the plastic layer from the mask portions 32.
As shown in FIGS. 5A to 5F, the method for manufacturing the vapor
deposition mask 30 first prepares a substrate 32K of a mask sheet
32S (see FIG. 5A). The substrate 32K of the mask sheet 32S includes
a metal sheet 32S1, which is an example of a metal plate for
forming a mask sheet 32S, and also a plastic layer 41 and a glass
substrate 42, which support the metal sheet 32S1. Then, the
thickness of the metal sheet 32S1 is reduced (see FIG. 5B). The
thickness of the metal sheet 32S1 is preferably reduced to half or
less the thickness of the metal sheet 32S1 before etching. A resist
layer PR is formed on the mask front surface 32F of the metal sheet
32S1 (see FIG. 5C). The resist layer PR is then exposed and
developed, thereby forming a resist mask RM on the mask front
surface 32F (see FIG. 5D).
Then, the mask front surface 32F of the metal sheet 32S1 is
wet-etched using the resist mask RM, forming a plurality of mask
holes 32H in the metal sheet 32S1 (see FIG. 5E). In the wet etching
of the metal sheet 32S1, front surface openings H1 are first formed
in the mask front surface 32F, and back surface openings H2, which
are smaller in size than the front surface openings H1, are then
formed in the mask back surface 32R. Then, the resist mask RM is
removed from the mask front surface 32F, completing a mask portion
32 formed of the mask sheet 32S (see FIG. 5F).
The step of preparing the substrate 32K includes a first joining
step. The first joining step sandwiches the plastic layer 41
between the metal sheet 32S1 and the glass substrate 42 and joins
the metal sheet 32S1 to the glass substrate 42 with the plastic
layer 41 in between. To join the metal sheet 32S1, the plastic
layer 41, and the glass substrate 42 together, a chemical bonding
(CB) process is first applied to the surfaces of the metal sheet
32S1 and the glass substrate 42 that are brought into contact at
least with the plastic layer 41. The surfaces of the metal sheet
32S1 and the glass substrate 42 that are subjected to the CB
process are target surfaces. In the CB process, a chemical solution
may be applied to the target surfaces to provide the target
surfaces with a functional group reactive with the plastic layer
41. For example, the CB process applies a hydroxyl group to the
target surfaces. The metal sheet 32S1, the plastic layer 41, and
the glass substrate 42 are layered in this order and subjected to
thermocompression bonding. The functional group on the target
surfaces reacts with the functional group on the surfaces of the
plastic layer 41, thereby bonding the plastic layer 41 to the metal
sheet 32S1 and to the glass substrate 42. In the first joining
step, the metal sheet 32S1 that is joined to the glass substrate 42
with the plastic layer 41 in between preferably has a thickness of
greater than or equal to 10 .mu.m.
The plastic layer 41 is preferably made of polyimide. This allows
the metal sheet 32S1, the plastic layer 41, and the glass substrate
42 to have similar thermal expansion coefficients. Consequently, in
the process of manufacturing the vapor deposition mask 30, the
laminate of the metal sheet 32S1, the plastic layer 41, and the
glass substrate 42 is unlikely to warp when heated, which would be
otherwise caused by a difference in thermal expansion coefficient
between the layers of the laminate.
Electrolysis or rolling is used to produce the metal sheet 32S1.
The metal sheet 32S1 obtained by electrolysis or rolling may be
subjected to post-treatment, such as polishing or annealing.
When electrolysis is used to produce the metal sheet 32S1, the
metal sheet 32S1 is formed on the surface of the electrode used for
electrolysis. The metal sheet 32S1 is then removed from the surface
of the electrode. The metal sheet 32S1 is thus produced.
When rolling is used to produce the metal sheet 32S1, the metal
sheet 32S1 preferably has a thickness of greater than or equal to
15 .mu.m. When electrolysis is used to produce the metal sheet
32S1, the metal sheet 32S1 preferably has a thickness of greater
than or equal to 10 .mu.m
The electrolytic bath for electrolysis contains an iron ion source,
a nickel ion source, and a pH buffer. The electrolytic bath may
also contain a stress relief agent, an Fe.sup.3+ ion masking agent,
and a complexing agent, for example. The electrolytic bath is a
weakly acidic solution having a pH adjusted for electrolysis.
Examples of the iron ion source include ferrous sulfate
heptahydrate, ferrous chloride, and ferrous sulfamate. Examples of
the nickel ion source include nickel (II) sulfate, nickel (II)
chloride, nickel sulfamate, and nickel bromide. Examples of the pH
buffer include boric acid and malonic acid. Malonic acid also
functions as an Fe.sup.3+ ion masking agent. The stress relief
agent may be saccharin sodium, for example. The complexing agent
may be malic acid or citric acid. The electrolytic bath used for
electrolysis may be an aqueous solution containing additives listed
above. The electrolytic bath is adjusted using a pH adjusting agent
to have a pH of between 2 and 3 inclusive, for example. The pH
adjusting agent may be 5% sulfuric acid or nickel carbonate.
The conditions for electrolysis are set to achieve desired values
of thickness and composition ratio of the metal sheet 32S1. These
conditions include the temperature of the electrolytic bath, the
current density, and the electrolysis time. The temperature of the
electrolytic bath may be between 40.degree. C. and 60.degree. C.
inclusive. The current density may be between 1 A/dm.sup.2 and 4
A/dm.sup.2 inclusive. The anode used in the electrolytic bath may
be a pure iron plate or a nickel plate, for example. The cathode
used in the electrolytic bath may be a plate of stainless steel
such as SUS304.
When rolling is used to produce the metal sheet 32S1, a base
material for manufacturing the metal sheet 32S1 is first rolled.
The rolled base material is annealed to obtain the metal sheet
32S1. When the base material, which is to be rolled to form the
metal sheet 32S1, is formed, a deoxidizer is mixed into the
constituents of the base material for rolling so as to remove the
oxygen trapped in the constituents. The deoxidizer may be granular
aluminum or magnesium. The aluminum or magnesium reacts with the
oxygen in the base material and is contained in the base material
as a metallic oxide such as an aluminum oxide or a magnesium oxide.
While most of the metallic oxide is removed from the base material
before rolling, some of the metallic oxide remains in the base
material to be rolled. In this respect, a method for manufacturing
the mask portion 32 using electrolysis limits mixing of the
metallic oxide into the mask sheet 32S.
The thinning step etches the metal sheet 32S1 to reduce the
thickness of the metal sheet 32S1 before the metal sheet 32S1 forms
the mask portion 32. The thinning step may use wet etching. The
thinning step preferably reduces the thickness of the metal sheet
32S1 to half or less the thickness of the metal sheet 32S1 before
thinning. This allows the metal sheet 32S1 used in the first
joining step to be at least twice as thick as the mask portion 32.
Thus, even when the mask portion 32 is required to have a thickness
of less than or equal to 15 .mu.m as described above, the metal
sheet 32S1 that has a higher rigidity than the mask portion 32 of
the vapor deposition mask 30 is used before the metal sheet 32S1 is
joined to the glass substrate 42 in the first joining step. This
facilitates the joining of the metal sheet 32S1 to the glass
substrate 42 as compared to a configuration in which the metal
sheet 32S1 that is joined to the glass substrate 42 has the same
thickness as the mask portion 32. The step of reducing the
thickness of the metal sheet 32S1 may be omitted.
In the thinning step, any acidic etchant may be used as the etchant
for wet-etching the metal sheet 32S1. When the metal sheet 32S1 is
made of Invar, any etchant can be used that is capable of etching
Invar. The acidic etchant may be a solution containing perchloric
acid, hydrochloric acid, sulfuric acid, formic acid, or acetic acid
mixed in a ferric perchlorate solution or a mixture of a ferric
perchlorate solution and a ferric chloride solution. The metal
sheet 32S1 may be etched by a dipping method, a spraying method, or
a spinning method.
An acidic etchant may be used to form a plurality of mask holes 32H
in the metal sheet 32S1 by etching. When the metal sheet 32S1 is
made of Invar, any of the etchants that are usable in the thinning
step described above can be used. In addition, any of the methods
usable in the thinning step may be used to etch the mask front
surface 32F.
As described above, when the thickness of the metal sheet 32S1 is
between 3 .mu.m and 5 .mu.m inclusive, a plurality of mask holes
32H may be formed such that 700 or more and 1,000 or less mask
holes 32H are arranged per inch in a plan view of the mask front
surface 32F of the metal sheet 32S1. That is, a mask portion 32 is
obtained that can be used to form a display device having a
resolution of between 700 ppi and 1,000 ppi inclusive. In other
words, a plurality of mask holes 32H can be formed such that 700 or
more and 1,000 or less mask holes 32H are arranged per inch in the
direction along the mask front surface 32F of the mask portion
32.
Further, when the thickness of the metal sheet 32S1 is between 10
.mu.m and 15 .mu.m inclusive, a plurality of mask holes 32H may be
formed such that 300 or more and 400 or less mask holes 32H are
arranged per inch in a plan view of the mask front surface 32F of
the metal sheet 32S1. That is, a mask portion 32 is obtained that
can be used to form a display device having a resolution of 300 ppi
to 400 ppi inclusive. In other words, a plurality of mask holes 32H
can be formed such that 300 or more and 400 or less mask holes 32H
are arranged per inch in the direction along the mask front surface
32F of the mask portion 32.
The step of preparing the substrate 32K may include a step of
thinning the metal sheet 32S1 from one surface of the metal sheet
32S1 before the first joining step. In this case, the thinning step
included in the step of preparing the substrate 32K is a first
thinning step, and the thinning step performed after the step of
preparing the substrate 32K is a second thinning step.
The metal sheet 32S1 includes a first surface and a second surface,
which is opposite to the first surface. In the first thinning step,
the metal sheet 32S1 is thinned by etching on the first surface. In
the second thinning step, the metal sheet 32S1 is thinned by
etching on the second surface. The surface formed by etching on the
first surface is the surface of the metal sheet 32S1 that is joined
to the plastic layer 41 and also subjected to the CB process.
Etching both the first and second surfaces of the metal sheet 32S1
allows the residual stress of the metal sheet 32S1 to be adjusted
from both the first and second surfaces. This limits imbalance in
the residual stress of the metal sheet 32S1 after etching, as
compared to a configuration that etches only the second surface.
Consequently, when the mask portion 32 obtained from the metal
sheet 32S1 is joined to the mask frame 31, the mask portion 32 is
less likely to have creases. The surface of the metal sheet 32S1
that is obtained by etching the first surface corresponds to the
mask back surface 32R of the mask sheet 32S, and the surface
obtained by etching the second surface corresponds to the mask
front surface 32F of the mask sheet 32S.
The amount of etching on the first surface of the metal sheet 32S1
is a first etching amount, and the amount of etching on the second
surface of the metal sheet 32S1 is a second etching amount. The
first etching amount and the second etching amount may be the same
or different. When the first etching amount differs from the second
etching amount, the first etching amount may be larger than the
second etching amount, or the second etching amount may be larger
than the first etching amount. When the second etching amount is
larger than the first etching amount, the amount of etching
performed while the metal sheet 32S1 is supported by the plastic
layer 41 and the glass substrate 42 is larger, increasing the
handleability of the metal sheet 32S1. This facilitates the etching
of the metal sheet 32S1.
In order to reduce the residual stress of the metal sheet 32S1 and
to reduce the metallic oxide contained in the metal sheet 32S1
obtained by rolling, the first etching amount and the second
etching amount are preferably greater than or equal to 3 .mu.m.
As shown in FIGS. 6A to 6C, the mask front surfaces 32F of the
outer edge sections 32E are joined to the inner edge sections 31E
(see FIG. 6A). Then, the glass substrates 42 joined to the
respective plastic layers 41 are peeled off from the plastic layers
41 (see FIG. 6B). The plastic layers 41 joined to the respective
mask portions 32 are then peeled off from the mask portions 32 (see
FIG. 6C). The vapor deposition mask 30 is thus obtained.
The step of joining a part of each mask portion 32 to a part of the
mask frame 31 includes a second joining step. The second joining
step joins the mask frame 31 to the surface of the mask portion 32
opposite to the surface that is in contact with the plastic layer
41. As described above, the mask frame 31 is preferably made of an
iron-nickel alloy, and the mask frame 31 is preferably at least
twice as thick as the mask portion 32. This enhances the mechanical
strength of the vapor deposition mask 30. Further, when vapor
deposition is performed using the vapor deposition mask 30, the
mask portion 32 is unlikely to warp, which would be otherwise
caused by a difference in thermal expansion coefficient between the
mask frame 31 and the mask portion 32. This avoids reduction in the
accuracy of the shape of pattern formed using the vapor deposition
mask 30.
As described above, when the thickness of the mask portion 32 is
between 3 .mu.m and 15 .mu.m inclusive, the thickness of the mask
frame 31 is preferably between 15 .mu.m and 200 .mu.m inclusive,
and the mask frame 31 is preferably at least twice as thick as the
mask portion 32. For the vapor deposition mask 30 including the
mask portions 32 usable to manufacture high-resolution display
devices, the thickness of each mask frame 31 is preferably at least
ten times thicker than the mask portion 32. For example, the
thickness of the mask portion 32 is preferably between 3 .mu.m and
5 .mu.m inclusive, and the thickness of the mask frame 31 is
preferably between 50 .mu.m and 200 .mu.m inclusive. Although the
mask portion 32 is extremely thin, the mask frame 31 that is at
least ten times thicker than the mask portion 32 avoids reduction
in the overall mechanical strength of the vapor deposition mask
30.
As described above, laser welding can be used to join the outer
edge section 32E to the inner edge section 31E. The section of the
mask portion 32 corresponding to the joining section 30BN is
irradiated with a laser beam L through the glass substrate 42 and
the plastic layer 41. As such, the glass substrate 42 and the
plastic layer 41 allow the laser beam L to pass through. In other
words, the laser beam L has a wavelength that can pass through the
glass substrate 42 and the plastic layer 41. Intermittent joining
sections 30BN are formed by applying the laser beam L
intermittently along the edge defining the mask frame hole 33. A
continuous joining section 30BN is formed by applying the laser
beam L continuously along the edge defining the mask frame hole 33.
The outer edge section 32E is thus welded to the inner edge section
31E. When the plastic layer 41 and the glass substrate 42 support
the mask portion 32 with stress acting on the mask portion 32
outward of the mask portion 32, the welding between the mask
portion 32 and the mask frame 31 does not have to involve
application of stress to the mask portion 32.
The method for manufacturing the vapor deposition mask 30 includes
a peeling step. The peeling step peels off the plastic layer 41 and
the glass substrate 42 from the mask portion 32. In the process of
manufacturing the vapor deposition mask 30, the plastic layer 41
and the glass substrate 42 support the mask portion 32 including
the mask holes 32H. In the vapor deposition mask 30, the mask frame
31 supports the mask portion 32. This allows the mask portion 32 to
be thinner than that in a configuration in which the vapor
deposition mask 30 consists only of the mask portion 32.
Accordingly, the shortened distance from one opening to the other
of each mask hole 32H improves the accuracy of the structure of the
pattern formed using the vapor deposition mask 30, while the
rigidity of the mask frame 31 improves the handleability of the
vapor deposition mask 30.
The peeling step includes a first peeling step and a second peeling
step. The first peeling step peels off the glass substrate 42 from
the plastic layer 41 by irradiating the interface between the
plastic layer 41 and the glass substrate 42 with the laser beam L
having a wavelength that passes through the glass substrate 42 and
is absorbed by the plastic layer 41.
The first peeling step applies the laser beam L to the interface
between the plastic layer 41 and the glass substrate 42 so that the
plastic layer 41 absorbs the heat energy of the laser beam L. This
heats the plastic layer 41 and weakens the strength of the chemical
bonding between the plastic layer 41 and the glass substrate 42.
The glass substrate 42 is then peeled off from the plastic layer
41. In the first peeling step, the entire joining section 30BN is
preferably irradiated with the laser beam L. However, only a part
of the joining section 30BN may be irradiated with the laser beam L
if the strength of bonding between the glass substrate 42 and the
plastic layer 41 is weakened in the entire joining section
30BN.
The glass substrate 42 preferably has a higher transmittance than
the plastic layer 41 at the wavelength of the laser beam L. This
increases the efficiency in heating the section of the plastic
layer 41 that forms the interface between the glass substrate 42
and the plastic layer 41, as compared to a configuration in which
the plastic layer 41 has a higher transmittance than the glass
substrate 42.
When the wavelength of the laser beam L is between 308 nm and 355
nm inclusive, for example, the glass substrate 42 preferably has a
transmittance of greater than or equal to 54%, and the plastic
layer 41 preferably has a transmittance of less than or equal to 1%
at this wavelength. As a result, more than half the light quantity
of laser beam L applied to the glass substrate 42 passes through
the glass substrate 42, and the plastic layer 41 absorbs most of
the laser beam L that has passed through the glass substrate 42.
This further increases the efficiency in heating the section of the
plastic layer 41 forming the interface between the glass substrate
42 and the plastic layer 41.
As described above, the plastic layer 41 is preferably made of
polyimide. In particular, the plastic layer 41 is preferably made
of a colored polyimide. The glass substrate 42 is preferably
transparent. Examples of the material used for the glass substrate
42 include quartz glass, non-alkali glass, and soda-lime glass.
After the first peeling step, the second peeling step peels off the
plastic layer 41 from the mask portion 32 by dissolving the plastic
layer 41 using a chemical solution LM. As the chemical solution LM,
a liquid may be used that can dissolve the material of the plastic
layer 41 and that is not reactive with the material of the mask
portion 32. The chemical solution LM may be an alkaline solution,
for example. The alkaline solution may be an aqueous sodium
hydroxide solution. The example shown in FIG. 6C uses a dipping
method to bring the plastic layer 41 into contact with the chemical
solution LM. However, a spraying method and a spinning method may
be used to bring the plastic layer 41 into contact with the
chemical solution LM.
In the process of peeling off the plastic layer 41 and the glass
substrate 42 from the mask portion 32, the first peeling step peels
off the glass substrate 42 from the plastic layer 41, and the
second peeling step peels off the plastic layer 41 from the mask
portion 32. This reduces the external force acting on the mask
portion 32, as compared to a configuration that applies external
force to the laminate of the glass substrate 42, the plastic layer
41, and the mask portion 32 to cause interface failure to peel off
the glass substrate 42 and the plastic layer 41 from the mask
portion 32. As a result, the peeling of the plastic layer 41 and
the glass substrate 42 is less likely to deform the mask portion
32, and ultimately less likely to deform the mask holes 32H in the
mask portion 32.
In the method of manufacturing a display device using the vapor
deposition mask 30 described above, the mask device 10 in which the
vapor deposition mask 30 is set is placed in a vacuum chamber of
the vapor deposition apparatus. At this time, the mask device 10 is
set in the vacuum chamber such that the mask back surface 32R faces
the vapor deposition target, such as a glass substrate, and that
the mask front surface 32F faces the vapor deposition source. Then,
the vapor deposition target S is placed in the vacuum chamber, and
the vapor deposition material is sublimated from the vapor
deposition source. This forms a pattern of the shape corresponding
to the back surface opening H2 on the vapor deposition target
facing the back surface opening H2. The vapor deposition material
may be an organic light-emitting material for forming pixels of a
display device, or a material of a pixel electrode for forming a
pixel circuit of a display device, for example.
Test Examples
Referring to FIGS. 7 to 9, test examples are now described. In
FIGS. 8 and 9, each region surrounded by the long dashed
double-short dashed line is a wavelength band of between 308 nm and
355 nm inclusive.
[Relationship between Laser Beam Wavelength and Pattern
Position]
First, test plates, which were thin metal plates, were prepared.
Each test plate had a central section and an outer section
surrounding the central section. In the test plate, the central
section had a plurality of patterns for measurement of the
positional accuracy, and the outer section was free of a pattern.
As the lasers to apply laser beams to test plates, a laser emitting
a laser beam having a wavelength of 1064 nm and a laser emitting a
laser beam having a wavelength of 355 nm were prepared.
Each laser emitted a laser beam to the outer section of each test
plate along one straight line. By applying a laser beam, a
plurality of irradiated sections each having a length of 0.1 mm
were formed at intervals of 0.5 mm. For each test plate, the state
before laser beam irradiation and the state after laser beam
irradiation were photographed using a CNC image measuring system
(VMR-6555, manufactured by Nikon Corporation). The amount of
displacement of the pattern closest to the outer section between
the test plate before irradiation and the test plate after
irradiation was determined.
As shown in FIG. 7, when a test plate was irradiated with a laser
beam of 1,062 nm, the amount of displacement was 2.7 .mu.m. When a
test plate was irradiated with a laser beam of 355 nm, the amount
of displacement was 0.27 .mu.m.
The first peeling step directs a laser beam toward the mask portion
through the glass substrate and the plastic layer. As such, the
glass substrate and the plastic layer absorb most of the laser beam
directed toward the mask portion. Nevertheless, the laser beam
directed toward the mask portion should not displace the pattern of
the mask portion in case the mask portion is irradiated with the
laser beam. For this reason, the laser beam used in the first
peeling step preferably has a wavelength of less than or equal to
355 nm.
[Transmittance of Glass Substrate and Plastic Layer]
Glass substrates A, B and C were prepared, and their transmittance
at each wavelength was measured. Glass substrate A was a quartz
glass substrate having a thickness of 2.3 mm (SMS6009E5,
manufactured by Shin-Etsu Chemical Co., Ltd.). Glass substrate B
was a non-alkali glass substrate having a thickness of 0.7 mm
(OA-10G, manufactured by Nippon Electric Glass Co., Ltd.). Glass
substrate C was a substrate made of soda-lime glass having a
thickness of 2.3 mm (soda-lime glass, manufactured by Central Glass
Co., Ltd.).
The transmittance of each glass substrate was measured using a
spectrophotometer (U-4100, manufactured by Hitachi, Ltd.). The
transmittances of the glass substrates were measured using a
wavelength range of between 200 nm and 800 nm inclusive and using
the transmittances in the atmosphere as reference values. FIG. 8
shows the measurement results of the transmittances of the glass
substrates.
As shown in FIG. 8, the transmittance of Glass substrate A was
observed to be substantially constant regardless of the wavelength
of light. The transmittance of Glass substrate B was observed to
rise sharply in a wavelength band of between 250 nm and 350 nm
inclusive. The transmittance of Glass substrate C was observed to
rise sharply in a wavelength band of between 300 nm and 350 nm
inclusive.
Plastic layers A, B and C were prepared, and their transmittance at
each wavelength was measured. Plastic layer A was a colored
polyimide plastic layer (Kapton (registered trademark) EN,
manufactured by DU PONT-TORAY CO., LTD.). Plastic layer B was a
colored polyimide plastic layer (Upilex (registered trademark) VT,
manufactured by Ube Industries, Ltd.). Plastic layer C was a
transparent polyimide plastic layer (Neoprim (registered
trademark), manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC.).
All the plastic layers had a thickness of 25 .mu.m.
The transmittance of each plastic layer was measured using a
spectrophotometer (same as above). In the same manner as the glass
substrates, the transmittances of the plastic layers were measured
using a wavelength range of between 200 nm and 800 nm inclusive and
using the transmittances in the atmosphere as reference values.
FIG. 9 shows the measurement results of the transmittances of the
plastic layers.
As shown in FIG. 9, the transmittances of Plastic layers A and B
were observed to rise sharply in a wavelength band of between 400
nm and 500 nm inclusive. In contrast, the transmittance of Plastic
layer C was observed to rise sharply in a wavelength band of
between 300 nm and 350 nm inclusive.
In the first peeling step described above, a laser beam having a
wavelength between 308 nm and 355 nm inclusive can be used.
According to the measurement results, at 308 nm, the transmittance
of Plastic layer A was 0.1%, the transmittance of Plastic layer B
was 0.0%, and the transmittance of Plastic layer C was 0.1%. At 308
nm, the transmittance of Glass substrate A was 92.7%, the
transmittance of Glass substrate B was 54.7%, and the transmittance
of Glass substrate C was 1.3%. At 355 nm, the transmittance of
Plastic layer A was 0.0%, the transmittance of Plastic layer B was
0.0%, and the transmittance of Plastic layer C was 85.1%. At 355
nm, the transmittance of Glass substrate A was 93.3%, the
transmittance of Glass substrate B was 86.5%, and the transmittance
of Glass substrate C was 83.4%.
In the first peeling step, in order to increase the efficiency of
the plastic layer in absorbing the laser beam, the transmittance of
the glass substrate is preferably higher than and significantly
different from the transmittance of the plastic layer at the
wavelength of the laser beam used in the first peeling step. In
this regard, when the wavelength of the laser beam is 355 nm, one
of Plastic layers A and B is preferably used as the plastic layer,
and one of Glass substrates A to C is preferably used as the glass
substrate. When the wavelength of the laser beam is 308 nm, one of
Plastic layers A to C is preferably used as the plastic layer, and
one of Glass substrates A and B is preferably used as the glass
substrate.
As described above, the present embodiment of a method for
manufacturing a vapor deposition mask has the following
advantages.
(1) In the process of manufacturing the vapor deposition mask 30,
the plastic layer 41 and the glass substrate 42 support the mask
portion 32 having a plurality of mask holes 32H. In the vapor
deposition mask 30, the mask frame 31 supports the mask portions
32. This allows the mask portion 32 to be thinner than that in a
configuration in which the vapor deposition mask 30 consists only
of the mask portion 32. Consequently, the shortened distance from
one opening to the other of each mask hole 32H improves the
accuracy of the structure of the pattern formed using the vapor
deposition mask 30, while the rigidity of the mask frame 31
improves the handleability of the vapor deposition mask 30.
(2) The external force acting on the mask portion 32 is reduced as
compared to a configuration that applies external force to the
laminate of the glass substrate 42, the plastic layer 41, and the
mask portion 32 to cause interface failure to peel off the glass
substrate 42 and the plastic layer 41 from the mask portion 32. As
a result, the peeling of the plastic layer 41 and the glass
substrate 42 is less likely to deform the mask portion 32, and
ultimately less likely to deform the mask holes 32H in the mask
portion 32.
(3) The plastic layer 41 has a lower transmittance than the glass
substrate 42. This increases the efficiency in heating the section
of the plastic layer 41 that forms the interface between the glass
substrate 42 and the plastic layer 41, as compared to a
configuration in which the plastic layer 41 has a higher
transmittance than the glass substrate 42.
(4) More than half the light quantity of laser beam L directed
toward the glass substrate 42 passes through the glass substrate
42, and the plastic layer 41 absorbs most of the laser beam L that
has passed through the glass substrate 42. This increases the
efficiency in heating the section of the plastic layer 41 that
forms the interface between the glass substrate 42 and the plastic
layer 41.
(5) The mask portions 32 and the mask frame 31 are both made of an
iron-nickel alloy, and the mask frame 31 is at least twice as thick
as the mask portions 32. This enhances the mechanical strength of
the vapor deposition mask 30.
(6) When the vapor deposition mask 30 is used for vapor deposition,
the mask portions 32 are unlikely to warp, which would be otherwise
caused by a difference in thermal expansion coefficient between the
mask frame 31 and the mask portions 32. This avoids reduction in
the accuracy of the shape of pattern formed using the vapor
deposition mask 30.
(7) Even when the thickness of the mask portion 32 is extremely
thin, the mask frame 31 that is at least ten times thicker than the
mask portion 32 avoids reduction in the overall mechanical strength
of the vapor deposition mask 30.
(8) The metal sheet 32S1 has a higher rigidity than the mask
portion 32 of the vapor deposition mask 30. This facilitates the
joining of the metal sheet 32S1 to the glass substrate 42 as
compared to a configuration in which the metal sheet 32S1 joined to
the glass substrate 42 has the same thickness as the mask portion
32.
(9) In the process of manufacturing the vapor deposition mask 30,
heating the laminate of the mask sheet 32S, the plastic layer 41,
and the glass substrate 42 is unlikely to warp the laminate, which
would be otherwise caused by a difference in thermal expansion
coefficient between the layers of the laminate.
(10) Etching the metal sheet 32S1 from the first and second
surfaces reduces the thickness of the metal sheet 32S1 and also the
residual stress of the metal sheet 32S1.
The above-described embodiment may be modified as follows.
The plastic layer 41 may be made from a plastic other than
polyimide as long as it is removable from the mask portion 32.
Nevertheless, to limit heat-induced warpage of the laminate of the
mask portion 32, the plastic layer 41, and the glass substrate 42,
the plastic layer 41 is preferably made of polyimide as described
above.
The metal sheet 32S1, which is joined to the glass substrate 42
with the plastic layer 41 in between in the first joining step, may
have a thickness of less than or equal to 30 .mu.m.
Provided that the mask frame 31 has a higher rigidity than the mask
portion 32, the mask frame 31 may have a thickness of less than or
equal to 50 .mu.m. Further, the mask frame 31 may be made of a
metal other than Invar.
The first peeling step may use a laser beam L that has a wavelength
of less than 308 nm or greater than 355 nm, as long as the
irradiation with the laser beam L can reduce the strength of
bonding between the plastic layer 41 and the glass substrate 42.
Further, the transmittances of the plastic layer 41 and the glass
substrate 42 for the laser beam L may be any values that allow the
laser beam L to be absorbed by the plastic layer 41 so as to weaken
the adhesion between the plastic layer 41 and the glass substrate
42. That is, the transmittance of the plastic layer 41 and the
transmittance of the glass substrate 42 for the laser beam L are
not limited to the values described above.
The first peeling step may be a step of peeling off the glass
substrate 42 from the plastic layer 41 by a method other than the
irradiation with the laser beam L. For example, the first peeling
step may use a chemical solution to peel off the glass substrate 42
from the plastic layer 41. Alternatively, the first peeling step
may physically peel off the glass substrate 42 from the plastic
layer 41 by applying an external force between the glass substrate
42 and the plastic layer 41.
The plastic layer 41 and the glass substrate 42 may be peeled off
from the mask sheet 32S at the same time. In other words, the
plastic layer 41 and the glass substrate 42 may be peeled off from
the mask sheet 32S in a single step. For example, the plastic layer
41 and the glass substrate 42 may be peeled off from the mask sheet
32S in a single step by using a chemical solution that dissolves
the plastic layer 41.
The mask holes 32H in the metal sheet 32S1 do not have to be formed
by wet etching using an etchant, and may be formed by applying
laser beams to the metal sheet 32S1.
DESCRIPTION OF THE REFERENCE NUMERALS
10 . . . Mask Device; 20 . . . Main Frame; 21 . . . Main Frame
Hole; 30 . . . Vapor Deposition Mask; 30BN . . . Joining Section;
31 . . . Mask Frame; 31E . . . Inner Edge Section; 31F . . . Frame
Front Surface; 31R . . . Frame Back Surface; 32 . . . Mask Portion;
32E . . . Outer Edge Section; 32F . . . Mask Front Surface; 32H . .
. Mask Hole; 32K . . . Substrate; 32R . . . Mask Back Surface; 32S
. . . Mask Sheet; 32S1 . . . Metal Sheet; 33 . . . Mask Frame Hole;
41 . . . Plastic Layer; 42 . . . Glass Substrate; H1 . . . Front
Surface Opening; H2 . . . Back Surface Opening; PR . . . Resist
Layer; RM . . . Resist Mask; S . . . Vapor Deposition Target; V . .
. Space
* * * * *